The present invention relates to a sheet distribution method and apparatus for performing sheet distribution operations such as collating and sorting.
Generally, a collating apparatus or collator for use with a copying machine has a plurality of sheet storing bins arranged one upon another and operates in a collation mode to distribute a set of copy sheets one by one into individual bins. The collator is also operable in a sorting or assortment mode in which copy sheets are fed or delivered successively into a single bin until a predetermined number is reached and then copy sheets are fed in the same way to the next bin.
A copying machine with such a collator is usually equipped with a stop switch to stop a copying operation or a series of copying cycles and an interrupt switch to interrupt or suspend a series of copying cycles halfway. With a copying machine having such switches, a copying operation or a series of copying cycles is usually determined as ended when the final copying action (a return of the optical unit) has been completed after the depression of the stop switch or the interrupt switch. Then the copying machine permits a copy start for another document or variation in the operating mode thereof, present number of sheets to be copied etc.
Further, the copying machine has such a design that there is a relatively long copy conveyance path including the copying machine body and collator. This inherent design brings about the following problem where sheets become jammed in such a conveyance path.
To make the description simple, suppose that an intended number of copies N is "9", that the 8th and 9th copy sheets or copies of the 5th page are travelling in the conveyance path in the collator, and that the 1st, 2nd and 3rd copies of the 6th page are moving simultaneously in the copying machine body.
When jamming occurs in the collator, the conveyance drive in the collator will be interrupted to allow only the three copy sheets or copies in the copying machine body to be discharged into a temporary discharge tray. The copy sheets in the collator on the other hand are wasted as jammed sheets. This is because it is quite difficult to exactly determine how many copies will be actually lost or to correlate the wasted copies with proper original documents. Thus, the 8th and 9th copies of the 5th page of the document are handled as jammed sheets. Accordingly, if manual insertion means or a feeder section is used in the above situation to cause the collator to collate the copies in the temporary discharge tray or the copying machine is energized, copies will be fed to the 8th and 9th bins of the collator in the wrong order, that is, the order of pages will be disrupted. This is because the copies in the temporary discharge tray or those fed from the copying machine body are not of the 5th page but of the 6th page.
In such a case, it is very troublesome to determine whether the jammed copies belong to the 5th page or the 6th page and the discrimination may become practically impossible depending on the construction of the collator. Furthermore, the operation must undertake quite intricate manipulation for re-loading the 5th document to re-copy it and then loading the 6th document to re-copy it.
Meanwhile, in a copying machine with an ADH, the ADH feeds documents one by one from a document tray to a copying position and, in this position, one copy or a series of copies are made. Thereafter, the document in the copying position is automatically returned to the tray while the next document if present is transferred to the copying position on a glass platen to undergo the same procedure.
A copying machine of the conventional design is operated for a high-speed continuous process such that a document on the glass platen is fed back to the document tray before the last copy thereof is delivered to a bin of the collator and the next document is fed to the glass platen. Accordingly, by the time jamming occurs in the collator during collation of the copies of the 1st page for example, the ADH will have already replaced the 1st document with the second despite the fact that the actual number of copies of the 1st page is short by the number of wasted copies, that is, the 1st document or page needs be re-copied to compensate for the shortage. This has heretofore been coped with by replacing the 2nd document with the 1st document.
It will thus be seen that the system which automatically returns a document by ADH in the event of jamming may damage valuable documents and renders the mechanism of the document handler disproportionately complex.
In this connection, a copy start may be permitted after the confirmation that the last copy sheet of a series of copy sheets of the same document page has reached a certain bin in the collator. It will be seen, however, that this method is disadvantageous in the following aspect.
The copying machine is operable not only in the described assortment or collation mode but in a usual or standard copying mode in which copy sheets from the copying machine will be simply stacked on a discharge tray instead of the delivery to the bins of the collator. This mode of operation is commonly employed to obtain copies of the same document page or those of a part of multiple different documents.
This means that in the usual copying mode the number of desired copy sheets is relatively small and, therefore, sheet jams can be dealt with easily compared with the collation and assortment modes. For this reason, it is needless in the usual copying mode to permit a copy start only after the last one of copy sheets of the same page has been found stored in a bin of the collator. Rather, it is desirable to give priority to the copying rate and allow the next copy start when the number of fresh sheets supplied (number of copy sheets of the same page) coincides with the present number of sheets to be copied.